1. Field of the Invention
The present invention generally relates to a method of transmitting music performance information based on MIDI (Musical Instrument Digital Interface) protocol through a communication satellite or Internet.
2. Description of Related Art
Recently, various attempts have been made for real-time transmission of music performance information composed of MIDI messages in a digital broadcasting system based on the Internet or the communication satellite (CS). The digital broadcasting of this type requires a protocol in taking account of a transfer error. MIDI is designed with special emphasis placed on the real-time capability. Therefore, use of MIDI in a great transfer error rate environment causes many problems. Especially, a serious problem is that a music note remains sounded unintentionally due to dropout or missing of note-on information during transfer of the music performance information. Action that can be taken is to mute all sounds upon detection of a data drop and to restart sounding upon reception of new note-on information. However, this measure frequently causes music interruptions in an environment prone to transfer error, leading to degraded service.
In the broadcasting service for transmitting music performance information, it is desired that music performance information can be reproduced from a midpoint of a music piece. In MIDI, timbre setting information and sound source control information are transmitted at the beginning of the music piece. Therefore, starting reproduction of the music piece after transmission of these pieces of information may result in the reproduction of a sound different from intended condition. In MIDI, besides the past state of timbre information, the past state of control change information of a sustain pedal, for example, affects current music reproduction. Therefore, it is necessary for the halfway reproduction to take measures against this problem.
Further, the physical transfer rate of MIDI is 31.25 kbps. The substantial data rate of music performance information is often far lower than the physical transfer rate. In an environment of a limited transmission band, data rate reduction is also an important point. Therefore, it is necessary for the music performance information transmitting system to flexibly cope with any environment in which the transmission band varies real-time like the Internet.
Thus, the conventional music performance information transmitting system has the following three problems: (1) reproduction of music performance is seriously affected in an environment suffering from a high transfer error rate; (2) reception of music performance information from a midpoint in a music stream hinders reproduction of the music performance; and (3) no transmission can be made at a rate capable of clearing a predetermined transfer bit rate.